Why Is My Car Hard to Start?

What does "hard to start" usually mean?

"Hard to start" covers a few different things, and sorting out which one you have saves money. Watch and listen the next time you turn the key or press the start button.

• Slow crank. The engine turns over sluggishly, like it is struggling, then may or may not start. This usually points to the battery, its cables, or the starter.
• Normal crank, slow to fire. The engine spins at a normal speed but takes a long time to catch, or catches and stumbles. This points toward fuel, spark, or sensor problems.
• Clicks or nothing. You hear a click or see dash lights but the engine does not turn. That is a battery, connection, starter, or security problem.
• Only when cold, or only when hot. Timing matters. A problem that shows up only on cold mornings or only after a short stop narrows the list.

Is it safe to drive a car that is hard to start?

Once it is running normally, the bigger risk is getting stranded, not the drive itself. A car that barely starts today may not start at all tomorrow, often at a bad time. But some signs mean you should not drive:

• If you smell strong raw fuel, or the check engine light flashes after the engine starts, do not drive the car; have it checked first. A flashing light means a misfire bad enough to damage the catalytic converter. Our guide to a flashing check engine light explains why.
• The engine shakes hard or stalls. If it runs very roughly after a hard start, see our guide to rough idle before you drive it far.
• Warning lights for charging or temperature. A battery light while driving can mean the alternator is not charging, which leads to the next hard start.

One more safety rule for cold mornings: do not warm up or test-crank the car inside a closed garage. The CDC says never to run a car or truck inside a garage attached to a house, even with the garage door open ^[4].

What causes a car to be hard to start?

These are the common causes, roughly from the cheapest and most likely to the least. AAA lists the battery first among its reasons a car will not start, along with the alternator, starter, ignition switch, spark plugs, ground cable, fuses, fuel, fuel filter, fuel pump relay, timing belt, steering lock, key fob battery, and gear selector position ^[1].

Cause	Typical sign	Who can check it
Weak or old battery	Slow crank, worse on cold mornings	You, with a voltmeter or a free store test
Corroded or loose battery cables	Slow crank or clicks; white or green crust on terminals	You
Key fob battery low	Push-button car does not recognize the key	You
Low fuel or fuel pump not priming	Normal crank, no catch; no hum from the tank at key on	You can listen; a shop tests pressure
Worn spark plugs or a failing coil	Normal crank, slow catch, may misfire once running	You or a shop
Crankshaft or camshaft sensor	Cranks but will not start, often with a code	Shop
Coolant temperature sensor	Hard start only cold or only hot	You with live data; a shop to confirm
Starter or alternator	Click, slow crank, or a battery that keeps going flat	Shop
Security or immobilizer fault	Cranks or no crank, with a security light on	Dealer or shop
Timing belt or chain problem	Cranks with an unusual sound, will not start	Shop only

AAA says a battery should be considered for replacement once it has been 3 to 5 years since the last one, and that a healthy battery reads about 12.6 volts with the car off ^[1]. Innova, a diagnostic tool maker, gives the same 12.6 volt figure for a fully charged battery ^[2].

For engines that crank normally, Identifix notes that worn or contaminated spark plugs should be replaced, that a failing timing belt can put the valves at risk, and that immobilizing devices can malfunction and stop a car from starting ^[3].

How do you find the cause of a hard start?

Work from free checks to paid tests. Do not replace the starter or fuel pump until a test points to it; a weak battery can mimic both. Identifix's advice is to gather information from the vehicle piece by piece to narrow down the cause, and to check the battery before the starter ^[3].

1. Notice the pattern. Write down how it cranks, how long it takes to catch, and whether it happens cold, hot, or after sitting. This information helps a shop as much as any test.

2. Scan for codes. Innova recommends using an OBD2 scan tool to check for stored codes that could indicate sensor or computer problems ^[2]. Look at pending codes too. If you are new to this, see how to use an OBD2 scanner.

3. Check the battery. With the car off for a while, measure across the terminals, or have the battery tested at a parts store. Look for white or green corrosion and loose clamps. Wear eye protection near the battery, and follow your owner's manual if you need to jump-start the car.

4. Check the fuel. Make sure there is enough fuel. Turn the key to "On" without starting and listen near the tank for a short hum. Innova says that if you do not hear a sound, the pump may be faulty ^[2]. Fuses and the pump relay are worth a look before the pump itself.

5. Rule out the key. On push-button cars, try the spare fob or hold the fob where your manual says to. AAA notes that a depleted fob battery can keep the car from recognizing it ^[1]. Make sure an automatic is fully in Park.

6. Let a shop test the rest. Fuel pressure, spark, crank and cam sensors, starter current draw, and compression need tools and know-how. High-pressure fuel systems in particular are not a do-it-yourself job; have a qualified technician check them. Crank in short tries rather than holding the key for a long time, so you do not drain the battery or overheat the starter.

Which check engine codes can show up with a hard start?

Often none. A weak battery or a tired starter does not usually set a code. But when the cause is fuel, spark, or a sensor, codes often appear. Misfire codes such as P0300 or P0301 can follow a hard start caused by worn plugs or a weak coil. A lean code like P0171 can point to low fuel pressure or an air leak. A coolant temperature code such as P0128 means the engine computer may be getting the wrong idea about engine temperature, which affects how much fuel it uses for a start. You can look up any other code with our code lookup tool.

What does it cost to fix a hard start?

It depends entirely on the cause, which is why diagnosis comes first. We do not list prices because we could not find a reliable, current U.S. source that covers this range of repairs. What drives the cost:

• The part. A key fob battery or cleaning battery terminals costs very little. A battery, starter, or fuel pump is a larger repair.
• Access. Some starters and fuel pumps are easy to reach; others mean removing other parts or dropping the fuel tank.
• Diagnostic time. An intermittent hard start, one that happens only sometimes, can take longer to catch.
• Doing it in order. Testing the battery first keeps you from buying a starter you did not need.